The present paper studies the general characteristics and evaluates the optimum performance of a simple two-stage compression partial oxidation gas turbine (POGT) cycle that has been combined with a Rankine cycle. The controlling parameters of the combined cycle that give optimum performance are determined and fitted into functional correlation equations. The values of the first-law efficiency and the second-law efficiency (eta(I) and eta(II), respectively) for the combined cycle are compared with those obtained for single POGT cycles. The effects of irreversibilities of the different units of the cycles are considered in the study. The combination of a POGT cycle with the Rankine cycle has achieved a maximum enhancement in net work output of similar to28.76% and optimum values of eta(I) approximate to 58% and eta(II) approximate to 80%. The present findings can form a very important basis for a complete phenomenological design of a combined POGT/Rankine cycle to achieve optimum performance.